Noninvasive retinal scan shows signs of early stages

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En español | A noninvasive scan that measures the width of blood vessels in the back of the eye shows promise as a way to help diagnose Alzheimer's disease in its early stages, an Australian researcher reports.

Shaun Frost, a scientist at the Australian e-Health Research Center, found that blood vessel changes in the light-sensitive tissue of the retina reflect an accumulation of amyloid plaque in the brain, thought to be an early sign of Alzheimer's.

"We're seeing signs of the plaque burden increasing in the brain a long time before we see the cognitive deficits of Alzheimer's disease," Frost said during a presentation at the 2011 Alzheimer's Association International Conference in Paris last month.

Frost measured the size of the retinal arteries and veins, then calculated a ratio between the two. He found that in people with Alzheimer's disease, the veins get smaller and the arteries appear to get bigger, proportionately.

"The artery-to-vein ratio in the retina was higher in Alzheimer's disease," Frost told the conference. And, he said, "if we look specifically at just the veins, we see a thinning of those in Alzheimer's disease."

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Frost scanned the eyes of 13 older people diagnosed with Alzheimer's and 13 with mild cognitive impairment, comparing them with healthy people. "It's not likely this test would be a stand-alone, definitive test for Alzheimer's disease," he said. But, he added, it could be used in conjunction with other new, very expensive screening tests.

William Klunk, M.D., an Alzheimer's expert at the University of Pittsburgh, agreed, saying in a discussion at the conference that current tests — special scans and spinal taps used to detect Alzheimer's-related changes in the brain — are a bit too invasive and expensive for widespread use as screening tools. He pointed out, however, that Frost's test uses equipment you'd find in any optometrist's office, simply measuring the width of the blood vessels.